I've been reading way too many Do The Math posts recently, and oddly enough, read this one on space mining about a week before the announcement. I've yet to sit down and crunch the numbers myself, but it's sobering.

I've been reading way too many Do The Math posts recently, and oddly enough, read this one on space mining about a week before the announcement. I've yet to sit down and crunch the numbers myself, but it's sobering.

lol

Quote:

Let’s say you arrived in Jupiter orbit running on fumes, relying on the gassy giant to restock your coffers. In order to get close enough to Jupiter, you’ll be skimming the cloud-tops at a minimum of 42 km/s. Getting 1 kg of fuel on board will require you to accelerate the fuel to the speed of your spacecraft, at a kinetic energy cost of 885 MJ. The energy content of methane is 13 kcal/g, or 54 MJ/kg. Oops. Not even enough to pay for itself, energetically. Get used to Jupiter. And I have completely ignored the fact that you need marry two O2 molecules to each molecule of methane, meaning you actually get only 11 MJ per kilogram of total fuel. Utterly hopeless.

Quote:

To get this asteroid moving at 5 km/s with conventional rocket fuel (or any “fuel” that involves spitting the mass elements/ions out at high speed) would require a mass of fuel approximately twice that of the asteroid. As an example, using methane and oxygen, (4 kg of O2 for every 1 kg of CH4), we would require two years’ of global natural gas production to be delivered to the asteroid (now multiply this by a large factor for the fuel to actually deliver it from Earth’s potential well). The point is that we would be crazy to elect to push the asteroid our way with conventional rockets.

Given that they don't seem to want to return anything to the surface initially, but merely park it in (possibly) a cislunar orbit, beneficiaries would primarily be government or private space entities. Investors seeking materials returns would have to wait for a few more decades.

I have zero faith in them moving anything from one part of our solar system to another part in a fashion that is both economically feasible and remotely beneficial within the next 100 years, unless a new form of power generation/collection is developed.

I've been reading way too many Do The Math posts recently, and oddly enough, read this one on space mining about a week before the announcement. I've yet to sit down and crunch the numbers myself, but it's sobering.

Virogtheconq wrote:

I've been reading way too many Do The Math posts recently, and oddly enough, read this one on space mining about a week before the announcement. I've yet to sit down and crunch the numbers myself, but it's sobering.

Sorry, but the guy is full of shit. Of course, nothing adds up if you use puny chemical rockets

All of this only works with Ion engines, and the best can now achieve a specific impulse of 8000-9000s. That is a mindbogglingly huge difference. Using the Tsiolkovsky rocket equation:

This may look horrible, but say you need 2km/s of delta-v and your Isp_1 is 450 and Isp_2 is 9000, this works out quickly as:

With Ion engines you only need one 25th the mass of propellant! So all of those examples by that idiot posturer would suddenly work!

Long story short:Tugging asteroids within our solar system with ion engines is a perfectly feasible proposition. Just don't bet on the asteroid arriving anytime soon. Also, don't bet on there being any profit to be made from such an asteroid. Even if it were made from pure gold or platinum.

Long story short:Tugging asteroids within our solar system with ion engines is a perfectly feasible proposition. Just don't bet on the asteroid arriving anytime soon. Also, don't bet on there being any profit to be made from such an asteroid. Even if it were made from pure gold or platinum.

1. Do they have functioning and tested space ion engines today?

2. Let's say they did manage to bring back a giant asteroid of pure gold or platinum, and it landed successfully in the ocean without causing any damage to the planet...

Wouldn't the value of the material plummet because they've effectively doubled the world's supply?

Yes. Hall effect ion thrusters are commonly used for stationkeeping and occasionally for orbit modification on communications satellites. Gridded ion thrusters have been used on a number of spacecraft including the Dawn mission currently orbiting the asteroid Vesta.

Long story short:Tugging asteroids within our solar system with ion engines is a perfectly feasible proposition. Just don't bet on the asteroid arriving anytime soon. Also, don't bet on there being any profit to be made from such an asteroid. Even if it were made from pure gold or platinum.

1. Do they have functioning and tested space ion engines today?

2. Let's say they did manage to bring back a giant asteroid of pure gold or platinum, and it landed successfully in the ocean without causing any damage to the planet...

Wouldn't the value of the material plummet because they've effectively doubled the world's supply?

The idea is to get asteroids with water/minerals/gasses etc near Earth, so you can use them to build things in space.

So rather than trying to get materials into space from Earths gravity well or trying to sell minerals on Earth, you essentially bring the materials locally and make your bigger/better spacecraft from them.

Ie the goal is not pure profit, it's cheaper space exploration which will lead to space technologies and things like missions to Mars.

Well, I guess I don't have to crunch the numbers myself now. I knew he was way off with the chemical rockets bit, but didn't have the inclination to look up the stats for ion engines at the time. Bigger benefit than I'd thought.

There's much more interesting things one can do if you want to extend the return time even further (the assumption about Hohmann transfers isn't always accurate - like with the [url=http://en.wikipedia.org/wiki/Interplanetary_Transport_Network]ITN[/rul]), but that runs into other economic challenges.

Not only do they, they've moved on from the initial versions, and advances in solar power have been seriously boosting their performance. The Dawn mission previously mentioned has enough reaction mass on board for an overall delta-v of >10 km/s, which is similar to what a multi-stage, multi-hundred-foot rocket does when it goes to orbit.

Though this is not based on anything, I hypothesize that as technology improves where we can gather vast quantities of solar energy and turn it more efficiently into electricity, projects such as mining NEO asteroids will be limited only by our imaginations.

I think the most cost effective idea is to get small asteroids and redirect them to enter earth's atmosphere and land in an easily-reclamable spot (i.e. shallow ocean). Then hoist them to the surface and melt them down. That might conceivably be profitable and not hugely risky if we're talking small asteroids. Anything that requires processing in-orbit seems like it could never be profitable to me. The amount of gold/platinum/etc. you'd need to make it profitable would instantly make the price of gold/platinum on Earth crater (pun intended) so it's no longer profitable. You can't just go and mine thousands of tons of platinum and expect it to be worth something when you introduce that much onto the market. Kind of like the Spanish and New World gold.

I think the most cost effective idea is to get small asteroids and redirect them to enter earth's atmosphere and land in an easily-reclamable spot (i.e. shallow ocean). Then hoist them to the surface and melt them down. That might conceivably be profitable and not hugely risky if we're talking small asteroids. Anything that requires processing in-orbit seems like it could never be profitable to me. The amount of gold/platinum/etc. you'd need to make it profitable would instantly make the price of gold/platinum on Earth crater (pun intended) so it's no longer profitable. You can't just go and mine thousands of tons of platinum and expect it to be worth something when you introduce that much onto the market. Kind of like the Spanish and New World gold.

you are mad, do you understand how big these things are and what happens when one enters the atmosphere?

The idea is to get asteroids with water/minerals/gasses etc near Earth, so you can use them to build things in space.

So rather than trying to get materials into space from Earths gravity well or trying to sell minerals on Earth, you essentially bring the materials locally and make your bigger/better spacecraft from them.

Ie the goal is not pure profit, it's cheaper space exploration which will lead to space technologies and things like missions to Mars.

Pretty much. It makes manned space travel that much easier.

Weird how only recently we were all being told how it would all be too expensive...

I'm still interested in how you would breakup/mine/extract/refine such a huge rock in space, even if it contains huge amounts of materials you want the density might mean you have to process all of it.

A gravitational tether could probably get the job done with even less and neatly sidesteps a bunch of other problems that would be associated with trying to stick engines on an asteroid.

One would still require the same amount of propellant, due to conservation of momentum of the satellite - asteroid system. But yes, a gravitational tether would work excellently (actually ONLY) with a ion engine space craft.

I'm still interested in how you would breakup/mine/extract/refine such a huge rock in space, even if it contains huge amounts of materials you want the density might mean you have to process all of it.

What do you do, blow it to bits then sift the debris cloud?

Baby steps. One step at a time. One problem at a time.

Once the asteroid is in transit, one has lots of years time to think creatively on what to do with it. Think more about it as forming future opportunities.

Wouldn't the smartest place to push the asteroids to be the moon? No atmosphere to ablate materials, and really nothing of any import to worry about smashing up. Plus, then we get all sorts of readily mineable materials (nickel and iron, for example) with which to make building materials for our Moon Base!

Small asteroids, maybe, but it's less energetic to "park" them in orbit since anything exploiting them in the near term would also just need to achieve that cislunar orbit, rather than attempting a soft landing on their own (not to mention moving the material back into orbit). That being said, actually processing them would be far easier on the lunar surface, but that requires a significant capital outlay.

Wudan Master wrote:

DonRoberto wrote:

I think the most cost effective idea is to get small asteroids and redirect them to enter earth's atmosphere and land in an easily-reclamable spot (i.e. shallow ocean). Then hoist them to the surface and melt them down. That might conceivably be profitable and not hugely risky if we're talking small asteroids. Anything that requires processing in-orbit seems like it could never be profitable to me. The amount of gold/platinum/etc. you'd need to make it profitable would instantly make the price of gold/platinum on Earth crater (pun intended) so it's no longer profitable. You can't just go and mine thousands of tons of platinum and expect it to be worth something when you introduce that much onto the market. Kind of like the Spanish and New World gold.

you are mad, do you understand how big these things are and what happens when one enters the atmosphere?

The KISS study (and what PR is targeting) are too small to do any damage. From the first KISS link:

Quote:

A 7‐m diameter asteroid is too small to be considereda potentially hazardous object (PHO) Carbonaceous asteroids are expected to have thestrength of “dried mud” and will breakup harmlessly inthe Earth’s atmosphere The spacecraft will keep the asteroid on a non‐collisioncourse with Earth at all times The final destination is a high lunar orbit

I think the most cost effective idea is to get small asteroids and redirect them to enter earth's atmosphere and land in an easily-reclamable spot (i.e. shallow ocean). Then hoist them to the surface and melt them down. That might conceivably be profitable and not hugely risky if we're talking small asteroids. Anything that requires processing in-orbit seems like it could never be profitable to me. The amount of gold/platinum/etc. you'd need to make it profitable would instantly make the price of gold/platinum on Earth crater (pun intended) so it's no longer profitable. You can't just go and mine thousands of tons of platinum and expect it to be worth something when you introduce that much onto the market. Kind of like the Spanish and New World gold.

I think the most cost effective idea is to get small asteroids and redirect them to enter earth's atmosphere and land in an easily-reclamable spot (i.e. shallow ocean). Then hoist them to the surface and melt them down. That might conceivably be profitable and not hugely risky if we're talking small asteroids.

Thats what I was thinking. If these things are mostly iron, you could drop them in a shallow sea somewhere remote and then magnetically lift them back out. No idea if that would be remotely cost effective though.

The losses from re-entry would be pretty huge, and the environmental concerns of doing so are nontrivial. You'd need to be pretty damn sure of the composition of the asteroid.

Wikipedia says:

Objects with diameters of 5-10 m impact the Earth's atmosphere approximately once per year, with as much energy as the atomic bomb dropped on Hiroshima, approximately 15 kilotonnes of TNT.

So assuming we're talking about something in that size range the environmental concerns would appear to be reasonable, at least at global scale, while still dropping 1000s of tons of metal. I guess the question is how do you get it to hit the surface without exploding in the air and spreading out all over the place. How much would a reasonably good ~5-10m diameter heat shield weigh? Doesn't have to actually survive reentry, just make sure that the object doesn't disperse too high up off the ground.

Edit: Obviously the area it hits isn't going to do so well. Maybe a (seasonally) frozen bit of arctic ocean would work? That way the damage is mostly to sea floor, and the energy needed to melt ice diminishes the wave's force more rapidly. (talking out of my ass here, i don't know much about orbital reentry or asteroids)

I don't think you can preserve the asteroid without totally destroying whatever it lands on (and even then it'll be pulverized). Landing on the ground will result in destroying a large area somewhere--the biggest NIMBY case you can come up with. Landing it in the ocean is pointless--okay, now all your stuff is at the bottom of the ocean. If that was an economical situation to be in, we'd be mining the bottom of the ocean.

Landing it in the ocean is pointless--okay, now all your stuff is at the bottom of the ocean. If that was an economical situation to be in, we'd be mining the bottom of the ocean.

I was thinking water because it will greatly slow the objects speed prior to impact, and then you can hopefully magnetically dredge up the debris without having to excavate all the dirt that will be kicked up on top of the object as it burrows into the Earth's crust.